Synthesis of Trifluoromethylated 4<i>H</i>-Pyran and 4<i>H</i>-Thiopyran via Divergent Reaction of β-CF<sub>3</sub>-1,3-Enynes with β-Ketothioamides
Qin Zeng, Xinyu Huang, Mingqing Liu, Zongxiang Yu, Yuanjing Xiao
Abstract
A chemodivergent tandem intermolecular hydrocarbonation and intramolecular oxy- or thioheterocyclization sequence of β-CF3-1,3-enyne with β-ketothioamides (KTAs) leading to ring-trifluoromethylated 4H-pyran or 4H-thiopyran, respectively, by the combined use of AgNO3 as a catalyst and Et3N as a base was developed. A remarkable substituent effect was observed. The substituent on either the keto moiety or the nitrogen atom of β-ketothioamides has a great impact on the chemoselectivity. Enynes possessing electron-withdrawing aryl groups on the alkyne moiety are generally good candidates for the present transformation.
Topics & Concepts
ChemistrySubstituentMoietyIntramolecular forceThiopyranPyranIntermolecular forceAlkyneChemoselectivityMedicinal chemistryRing (chemistry)IsoxazoleStereochemistryArylCatalysisOrganic chemistryAlkylMoleculeFluorine in Organic ChemistrySynthesis and Catalytic ReactionsSynthesis of heterocyclic compounds